How do you specify the number of outputs for any LSTM layer in a Keras model in Python?

$1.$ model.add$($LSTM$($units$=64))$

$2.$ model.add$($LSTM$($output$\_$dim$=64))$

$3.$ model.add$($LSTM$($hidden$\_$units$=64))$

$4.$ model.add$($LSTM$($num$\_$units$=64))$